Not applicable.
1. Field of the Invention
This invention relates to apparatus adapted for use in a deep well as might be found in oil and gas exploration and production more particularly relates to an improved sliding sleeve valve installed on to a tube string.
2. Discussion of the Prior Art
Sliding sleeve valves are well known for deep down-hole applications in gas and oil exploration and production wells. Typically a sliding sleeve valve is used to control fluid flow between a string of tubing and the annulus between the tubing and the well wall. The flow of fluid through the sliding sleeve valve may be from hydrocarbon bearing strata to the surface in a production scenario. Alternatively, the flow of fluid may be from the surface into a particular hydrocarbon-bearing stratum for selective treatment for hydrocarbon recovery enhancement or well stimulation. In the latter application, a corrosive fluid such as an acid may be injected into hydrocarbon bearing strata to enhance hydrocarbon recovery. Alternatively, operating fluid may be applied to a hydrocarbon bearing strata under very high pressures to stimulate the well and enhance recovery.
The operation of such sliding sleeve valves are controlled by known wire line or hydraulic pressure actuated shifter tools. These tools selectively operate the sliding sleeve valve and lock it into a desired operating position at a desired depth in the well bore.
Examples of sliding sleeve valves can be found in U.S. Pat. No. 5,479,989 issued to Shy et al on Jan. 2, 1996 entitled xe2x80x9cSleeve Valve Flow Control Device with Locator Shifterxe2x80x9d, U.S. Pat. No. 5,211,241 issued to Mashaw et al on May 18, 1993 entitled xe2x80x9cVariable Flow Sliding Sleeve Valve and Positioning Shifting Tool Thereforexe2x80x9d, U.S. Pat. No. 5,183,114 issued to Mashaw et al on Feb. 2, 1993 entitled xe2x80x9cSleeve Valve Device and Shifting Tool Thereforexe2x80x9d and U.S. Pat. No. 6,044,908 issued to Wyatt on Apr. 4, 2000 entitled xe2x80x9cSliding Sleeve Valve and Seal Ring For Use Thereinxe2x80x9d.
Critical to the successful operation of a sliding sleeve valve in deep well operations is the integrity of the valve seals. Sliding sleeve valves are known to operate under extreme fluid pressures, temperatures and in corrosive environments. Known sliding sleeves have a variety of seal configurations but many still suffer from undesired leakage especially after they have undergone numerous opening and closing cycles. Known sliding sleeve valves have a single leak paths at the top and/or bottom segments. Therefore, there is an ongoing requirement for a sliding sleeve valve that eliminates this leak path and operates reliably and leak-free under a variety of operating conditions and after numerous opening and closing cycles.
The present invention provides for a sliding sleeve valve that can be easily installed at a well site without the need for special tools or training. The sliding sleeve valve of the present invention is capable of reliable and selective operation at extreme depths while maintaining leakage integrity after numerous opening and closing cycles.
The present invention comprises a sliding sleeve valve assembly having a tubular main body threadably attached to a tube string. A tubular closing sleeve is co-axially and slidably mounted within the tubular main body for axial movement therein. The tubular main body comprises a top, middle and bottom segments. These segments are threadably engaged with each other to make for easy installation without the need for special tools.
The middle segment of the main body and the closing sleeve both have fluid flow apertures. When the sliding sleeve valve is in the open position, the flow apertures in the closing sleeve are in communication with the fluid flow apertures in the middle segment of the main body permitting fluid flow across the valve. The fluid flow apertures in the closing sleeve and middle segment are sufficiently sized so that when they are in communication with each other, the total flow in the tube string can be accommodated through the communicating apertures. The closing sleeve is attached to and controlled by a wire or hydraulic tool string. The sliding sleeve valve has a fully closed position, an equalizing position and a fully open position.
In operation, the tube string may be under greater pressure than the formation resulting in fluid flows across the open sleeve valve from the tube string to the formation. Alternatively, the formation may be under greater pressure than the tube string resulting in fluid flows across the open sleeve valve from the formation into the tube string. When the sleeve valve is closed, the resulting pressure differential across the valve may result in leakages into or out of the sleeve valve along a pathway that is generally defined along those areas where the top, middle and bottom segments come together. My invention provides for triple seal redundancy to seal the leakage pathway in both directions across the closed sleeve valve.
Another aspect of the invention is the controlled equalization feature that equalizes pressure across the valve during opening and closing operations. This reduces pressure and stress on the seals which assists them in maintaining their leakage integrity over multiple opening and closing operations. In addition the controlled pressure equalization reduces operation problems with the shifting tool string. The equalization feature comprises a plurality of equalization ports set radially in the closing sleeve. In operation and when opening the sliding sleeve valve, the equalization ports will be in communication with the fluid flow apertures of the middle segment of the main body for a predetermined amount of time and before the fluid flow apertures of the closing sleeve come into communication with the fluid flow apertures of the middle segment. This permits fluid pressures to equalize across the valve body so that seal pressures are reduced and resistance offered to the shifting tool caused by the pressure differential across the valve body is also reduced. When the sleeve valve is being closed, the equalization ports will remain in communication with the apertures of the middle segment after the apertures of the closing sleeve are non-communicative thereby permitting a gradual change in pressure over the body of the sleeve valve. The equalization ports also relieve trapped pressure between the seals when the valve is fully opened or closed. This reduces the instances of xe2x80x9cpressure lockxe2x80x9d during repeated opening and closing operations of the valve.
Accordingly, several objects and advantages of my invention are set out below.
A principal object of my invention is to provide a sliding sleeve valve that has an improved triple redundancy configuration to resist leakage between the tubing and the annulus after numerous opening and closing cycles.
It is an object of my invention to provide an improved sliding sleeve valve that can be easily installed at the well site without the need for special tools or operator skills.
It is another object of my invention to provide a sliding sleeve valve that is capable of selective and reliable operating at extreme depths within a well hole under a variety of operating conditions.
Yet another object of my invention is to provide a sliding sleeve valve that can be easily adapted to cold weather operations, hot well conditions and varying well conditions.
Still another object of my invention is to provide an improved sliding sleeve valve with a fluid pressure equalization feature.
Another object of my invention is to provide a sliding sleeve valve that permits the release of trapped pressure between the seals and prevents the occurrence of pressure lock during valve operation.
The above and other objects of my invention will become clear from the drawings, detailed description and claims appended hereto.